A former stripper accused of plotting the murders of her hotel-heir husband and his elderly mother also schemed to snuff out a witness in the case, a prosecutor said today.

The latest bombshell in the gruesome bludgeoning death of millionaire Ben Novack Jr. came as his widow, Narcy Novack, 53, appeared in White Plains federal court and pleaded not guilty in her husband’s July 2009 slaying at the Hilton Rye Town.

“There was also a plot to kill another witness in the case,” prosecutor Elliott Jacobson told the judge as part of his bid to keep Novack, 53, behind bars until her trial.

Novack’s lawyer, Howard Tanner, asked Jacobson to cough up more details. Jacobson declined and didn’t name the witness.

Meanwhile, Tanner argued that Novack wasn’t a flight risk, noting, “My client allegedly committed these crimes a year ago. She’s had a passport the whole time and could have left the jurisdiction – but she didn’t.”

US Magistrate Judge Paul Davison ordered that Novack — who was recently brought to New York for trial from her home state of Florida—to continue being held without bail.

Ben Novack’s father founded Miami’s storied Fontainebleau hotel.

Prosecutors say Narcy Novack let two killers into her suite at the Hilton, where she and Ben were attending an Amway convention. She then allegedly watched as they pounded him with dumbbells, handed the thugs a pillow to muffle her husband’s screams, and ordered his attackers to cut out her husband’s eyes.

Narcy, a former dancer at a Florida strip club, suspected her husband was having an affair and was going to dump her, authorities have said.

Novack has also been accused — but not charged — in the April 2009 Florida slaying of her mother-in-law, Bernice. The 86-year-old woman was found dead in a trail of blood with her skull fractured and a broken jaw. A Florida medical examiner initially ruled the death accidental but the case was recently reopened.

Jacobson has said Bernice was brutally beaten with a monkey wrench, and that Narcy Novack orchestrated the attack.

Jacobson also reiterated yesterday his previous allegations that Novack was involved in a plot to plant drugs in the car of her adult daughter, May Abad, and have her attacked.

“There was a plot in Florida to plant guns and marijuana, and the plan was to assault the defendants’ daughter because they are in a heated contest over [Ben Novack’s] estate,” Jacobson said.

Narcy stood to inherit her Ben and Bernice’s estimated $10 million-plus fortune upon their deaths. After their deaths, Abad, whose sons are the next in line for the money, had teamed with Bernice’s sister to keep the money out of Narcy’s hands.

In court yesterday, Novack appeared solemn in a pale gray prison garb, her voice barely a whisper as she responded to questions from the judge.